Coated articles are known in the art for use in residential and commercial window applications including, for example, architectural glazings, insulating glass (IG) window units, vacuum insulated glass (VIG) units, etc. Coated articles also are oftentimes used in vehicle windows, refrigerator/freezer doors, etc. It is known that in certain instances, it is desirable to heat treat (e.g., thermally temper, heat bend, and/or heat strengthen) such coated articles for purposes of tempering, bending, or the like.
In certain situations, designers of coated articles often strive for a combination of good selectivity, desirable visible transmission, low emissivity (or emittance), and low sheet resistance (Rs). Low-emissivity (low-E) and low sheet resistance characteristics permit such coated articles to block significant amounts of infrared (IR) radiation so as to reduce, for example, undesirable heating of vehicle or building interiors. More particularly, low-E coatings may oftentimes be used to control the amount of solar and mid-IR radiation transferred from and into building structures, vehicles, etc. Emissivity in this context thus refers generally to the ability to radiate heat in the form of longer-wave radiation. The lower the emissivity, the better the insulating properties of the coated glazing tend to be.
Low-E coatings typically involve a glass substrate supporting an IR reflecting layer that is sandwiched between one or more dielectric layers. It is not uncommon for some coated articles to include one, two, three, or four, IR reflecting layers, with each IR reflecting layer being separated by one or more dielectric layers, and with there being one or more dielectric layers provided below the lowest and above the upper IR reflective layers. Silver is one common IR reflecting layer used in low-E coatings.
Low-E coatings are typically deposited at room temperatures to reduce the likelihood of unwanted agglomeration in the silver layer. Agglomeration could be problematic from both functional and aesthetic standpoints. Unfortunately, however, the performance of such room-temperature deposited coatings is not optimal, with emissivity generally ranging between 0.035 and 0.040 for single-Ag coatings, and between 0.022 and 0.027 for double-Ag coatings.
To lower the emissivity, the coatings are often subjected to post-deposition thermal activation, with or without tempering (generally achieved by a forced quenching of the glass by air). Emissivity of thermally activated products oftentimes can range from 0.028 to 0.032 for single-Ag coatings, and from 0.019 to 0.023 for double-Ag coatings. Overexposure to thermal activation often results in the loss of film smoothness due to silver agglomeration before reaching the minimum emissivity possible. There also is oftentimes a trade-off between low-E performance and desired visual properties (e.g., in terms of visible transmission, etc.). It thus will be appreciated that there is room for performance improvements when it comes to activating low-E coatings.
Another currently available activation technique uses the exposure of a low-E coating to high-intensity flash light. Such radiative heating of the coating also results in reduced emissivity compared to the as-deposited coating. One concern with this approach, however, is that the light sources used in the industry typically are optimized for traditional recrystallization of amorphous silicon (a-Si) and operate primarily in the near infrared spectrum (e.g. in the 800-1200 nm range). Coincidently, these frequencies are mostly reflected by the Ag coatings, because they overlap with the plasma wavelength region of the Ag, caused by the oscillation of free electrons induced by the infrared. The oscillation, which repels the near-IR photons, gets stronger as the process of the activation progresses or the energy of the light increases. Emissivity of the flash-light activated films typically ranges from 0.030 to 0.034 for single-Ag coatings, and from 0.020 to 0.024 for double-Ag coatings. Thus, it once again will be appreciated that there is room for performance improvement when it comes to activating low-E coatings, especially with this somewhat difficult to implement approach.
One aspect of certain example embodiments relates to improving the emissivity of low-E coatings, e.g., using a two-stage approach for activating room-temperature deposited silver-based low-E coatings. In certain example embodiments, it is possible to achieve levels of emissivity lower than those attainable using conventional activation methods, such as tempering and flash treatments alone.
Another aspect of certain example embodiments relates to one or more infrared reflecting layers being activated via a non-equilibrium preconditioning activation that uses photons with specific frequencies/frequency ranges, followed by a more equilibrium thermal activation.
Another aspect of certain example embodiments relates to using a flash activation that aids in rearranging the silver atoms to energetically favorable positions while helping to avoid their unwanted agglomeration, followed by a thermal activation that aids in aligning the chemical potentials of the layers of the layer stack and in further densification of the preconditioned silver layer.
Still another example embodiment relates to applying a preconditioning flash activation after each IR reflecting layer is deposited, followed by a thermal activation after all IR reflecting layers have been deposited (e.g., once all layers in the layer stack have been deposited).
Still another example embodiment relates to applying a series of preconditioning flash activations after all IR reflecting layers have been deposited (e.g., once all layers in the layer stack have been deposited), with different flash characteristics being used for the different flashes in the series to in essence target the different IR reflecting layers, followed by a thermal activation.
Still another example embodiment relates to applying a series of preconditioning flash activations, with flash activation for the top IR reflecting layer(s) being performed using a flash source disposed above the coating and with flash activation for the bottom IR reflecting layer(s) being performed using a flash source disposed below the coating, followed by a thermal activation.
In certain example embodiments, a method of making a coated article including a multilayer thin film low-E coating supported by a glass substrate is provided. The low-E coating is formed on the substrate, with the low-E coating including at least first and second IR reflecting layers comprising silver, and with each of the first and second IR reflecting layers being sandwiched between one or more dielectric layers. The first IR reflecting layer is farther from the substrate than the second IR reflecting layer. Each of the IR reflecting layers is activated using a two-stage treatment. The first stage in the treatment preconditions the IR reflecting layers via flash light source exposure in at least first and second wavelength ranges, with the first wavelength range preferentially transmitting energy to the first IR reflecting layer and the second wavelength range preferentially transmitting energy to the second IR reflecting layer. The second stage in the treatment is a thermal treatment that is performed after all of the IR reflecting layers have been deposited, directly or indirectly, on the substrate. The second stage follows the first stage.
According to certain example embodiments, the first stage may be performed each time one of the IR reflecting layers is deposited, directly or indirectly, on the substrate, and prior to the subsequent IR reflecting layer being deposited. The first and second wavelength ranges may, for instance, be the same.
According to certain example embodiments, the first stage may be performed after all of the IR reflecting layers are deposited, e.g., with the first and second wavelength ranges being different from one another. For instance, the first wavelength range may have a maximum intensity in a first area proximate to a maximum absorptivity of the first IR reflecting layer, and the second wavelength range may have a maximum intensity in a second area that is remote from the first area and where the absorptivity of the first IR reflecting layer is less than one-half of its maximum.
According to certain example embodiments, the first stage may be performed after all of the IR reflecting layers are deposited, and the first IR reflecting layer may be preconditioned using a first light source provided over the substrate and the second IR reflecting layer may be preconditioned using a second light source provided under the substrate.
In certain example embodiments, a method of making a coated article including a multilayer thin film low-E coating supported by a glass substrate is provided. The low-E coating is formed on the substrate, with the low-E coating including a plurality of room temperature sputter deposited IR reflecting layers comprising silver, and with each of the IR reflecting layers being sandwiched between one or more dielectric layers. Each of the IR reflecting layers is activatable using a two-stage treatment. The first stage in the treatment includes light source exposures with photons in flash light profiles selected to preferentially transmit energy to the IR reflecting layers based on respective absorption levels thereof. The second stage in the treatment includes exposure to temperatures in excess of 400 degrees C. following formation of the IR reflecting layers. At least the first stage in the treatment is performed for each of the IR reflecting layers.
In certain example embodiments, a coated article is provided. The coated article includes a glass substrate, and a multilayer thin film low-E coating supported by the substrate. The low-E coating includes a plurality of room temperature sputter deposited IR reflecting layers comprising silver, with each of the IR reflecting layers being sandwiched between one or more dielectric layers, and with each of the IR reflecting layers having been activated using a two-stage treatment. The first stage in the treatment includes light source exposures with photons in flash light profiles selected to preferentially transmit energy to the IR reflecting layers based on respective absorption levels thereof. The second stage in the treatment includes exposure to temperatures in excess of 400 degrees C. following formation of the IR reflecting layers. The emissivity of the coating is 0.011 or lower.
In certain example embodiments, a system for forming a coated article is provided. A sputtering apparatus is controllable to form a multilayer thin film low-E coating on a glass substrate, with the coating comprising a plurality of room temperature sputter deposited IR reflecting layers comprising silver, and with each of the IR reflecting layers being sandwiched between one or more dielectric layers. At least one flash light source is controllable to precondition the IR reflecting layers through exposures to photons using flash light profiles selected to preferentially transmit energy to the IR reflecting layers based on respective absorption levels thereof. The flash light profiles use photon energies of 0.82-3.55 eV and are sufficient to rearrange silver atoms in the IR reflecting layers to more energetically favorable positions without also causing over-agglomeration. Emissivity of the coating is further lowerable through exposure to a subsequent thermal process. For instance, the system may include a furnace configured to heat the substrate with the preconditioned IR reflecting layers thereon to a temperature of at least 400 degrees C. and reduce emissivity of the coating to 0.011 or lower.
The above-described and/or other coated articles may be included in insulating glass (IG) units in certain example embodiments. Certain example embodiments relate to such IG units, and/or methods of making the same.
The features, aspects, advantages, and example embodiments described herein may be combined to realize yet further embodiments.